Novel strategies for the synthetic manipulation of saccharide functional groups

The present PhD thesis deals with several synthetic aspects of carbohydrate chemistry, with a particular emphasis on the development of experimentally simplified protocols aimed both at protection/transformation of saccharide functional groups and at the construction of glycosidic linkages. Most of the current methods used for the synthetic manipulation of carbohydrates suffer from several drawbacks arising from the inconvenient experimental conditions needed in the reported procedures; these often entail the use of expensive or sensitive reagents, strictly anhydrous conditions, lengthy multi-step synthetic sequences and very often the use of toxic and high boiling solvents, thus making the preparation of building-blocks and the construction of glycosidic linkages highly tricky and time-consuming tasks. Works discussed in this thesis concern the implementation of streamlined methodologies for several synthetic elaborations of saccharide functional groups; a special focus is addressed to solvent-free protocols and their incorporation into synthetic schemes allowing multiple transformations to be performed under air and in a one-pot fashion. Some of the developed protocols are aimed at the regioselective and orthogonal protection of carbohydrates with several protecting groups such as, for example, acetal, trityl or silyl functionalities. Other methodologies are focused on several useful transformations of saccharide functional groups; among these, practical protocols for the preparation of glycosyl chlorides and their use as glycosyl donors into innovative glycosylation schemes are presented. A novel method for the immobilization of carbohydrates on surfaces through direct O-glycosylation has also been developed and discussed in the present thesis, since it provides a streamlined approach for the preparation of useful carbohydrate chips.